Some observations on the blink reflex in posttraumatic coma

Clinical Manifestation and Risk Factors Associated With Remission in Patients With Filamentary Keratitis

PURPOSE

This study investigated the clinical manifestation and risk factors associated with remission in filamentary keratitis.

DESIGN

Retrospective, interventional, comparative case series.

METHODS

We retrospectively reviewed the medical records of 116 patients with filamentary keratitis diagnosed and treated between January 2012 and December 2018. We investigated the 5 causative factors including brain lesion, dry eye syndrome, autoimmune disease, ocular surgery or injury, and other conditions; treatment methods and duration; and remission status, and analyzed the risk factors associated with remission.

RESULTS

The mean age of the patients was 56.9 ± 19.1 years and the mean follow-up duration was 14.9 ± 22.8 months. The most common underlying condition associated with filamentary keratitis was identified as a brain lesion (36.2%), followed by dry eye syndrome (30.2%) and autoimmune disease (24.1%). A comparison of remission rates among the causative factors revealed that cases associated with brain lesions had significantly lower remission rates (33.3%) than those associated with other causative factors (>60%) (P = .001). After adjustment for sex, age, diabetes mellitus, and hypertension, the treatment failure rate in patients affected by brain lesions was 6.602-fold higher than that associated without brain lesion (P = .001). The treatment method-dependent differences in the remission rate were observed in brain lesion and dry eye syndrome (P = .041 and P = .005, respectively).

CONCLUSIONS

The most common condition leading to filamentary keratitis was a brain lesion, followed by dry eye syndrome and autoimmune disease. The treatment failure rate was statistically significantly low only in patients with filamentary keratitis associated with brain lesions.

Making slaughterhouses more humane for cattle, pigs, and sheep

When a stunning method is being evaluated, it is essential that the animal-handling and restraint methods that are used with it are also examined. This makes it possible to determine the effect of the entire system on animal welfare. Cattle, pigs, and sheep will move easily through the races at a slaughter plant if visual distractions such as reflections on shiny metal, dangling chains, moving equipment, or people up ahead are removed. The most important scientific research on captive bolt, CO2, and electrical stunning methods is reviewed. A common mistake made by people evaluating insensibility is to misinterpret reflexive leg kicks as a sign of return to sensibility. When religious slaughter is being evaluated, the variable of how the animal is restrained must be separated from the variable of slaughter without stunning. Slaughter can be done with a high level of animal welfare.

A neurophysiological approach to brainstem reflexes. Blink reflex

The blink reflex (BR) is a generalised phenomenon in mammals. Its teleological protective eye function is perhaps the reason why the BR can be provoked by a multitude of stimuli. As corneal and glabellar reflexes, BR has an inveterate use in the neurological exploration. Some of its physiopathological aspects were discussed more than 100 years ago, and soon half a century will have passed since the first electrophysiological study was published. This review focuses on the BR elicited by the electrical stimulation of the trigeminal supraorbital nerve, a controlled and reliable model in clinical neurophysiology. The electrically elicited BR is an exteroceptive-nociceptive reflex recorded on the orbicularis oculi muscle and formed by three components: the two principal ones, R1 and R2, of well-known characteristics, and a third, R3, of increasing interest, to which there is wide mention. The trigeminal afferent limb reaches the facial efferent one by means of a long and quite complex central pathway located at the brainstem bulbopontine level. The anatomical substrate and criteria of the rich topographical lesional semiology of the BR are established. The importance of the suprasegmental influences upon the reflex, coming mainly from the cerebral cortex and basal ganglia, as well as the impairment caused by their damage, will be emphasised. Special attention is paid to the relationship between the reflex and the dopaminergic system, and the consequences of its derangement. The methods of habituation and suppression-recovery of the BR are extensively and critically reviewed. These methods measure its excitability and serve in practice for the pathophysiological study of numerous diseases. The relationship of the BR with the spontaneous blinking is considered, and the existence of a primary inhibitory reflex on levator palpebrae muscles, previous to the active reflex response of the orbicularis, is proposed. The electrophysiological characteristics of the glabellar reflex, the corneal reflex, the acoustic, photic and somatosensory provoked BR, the ontogeny, and some of the common factors influencing the reflex, such as sleep, are also discussed. The strategic position of the neural structures of the BR, in an area involved in the gating of the various sensory-motor systems and the relative ease to its evaluation with common methodology used in clinical neurophysiology, makes the BR an essential tool for the diagnosis and pathophysiological insight into an important number of human neurological disorders.

Corneal reflex responses to mechanical and electrical stimuli in coma and narcotic analgesia in humans

The corneal reflex, a bilateral eye-blink, can be elicited in humans either by mechanical or electrical corneal stimulation. Both in comatose patients and in normal subjects injected with the opiate fentanyl, the electrically-evoked corneal reflex was more suppressed than the mechanically-evoked reflex. We propose that the mechanical input yields a reflex more resistant to depression of the corticoreticular drive and to narcotic analgesia, because it exploits temporal summation at central synapses, whereas the electrical input exploits spatial summation.

Post-traumatic apallic syndrome following head injury. Part 1: clinical characteristics

Epidemiological studies made within the western countries indicate an incidence of 200-300 traumatic head injuries per 100 000 residents each year. Severe head injuries account for 5-25% of all head injuries; 10-14% of all severe head-injured patients develop into a vegetative state, in which a sleep-wake rhythm is apparent, but however in which there is no evidence of awakeness or reactivity to the environment. The most commonly used labels, in the German and international literature, for these patients are 'vegetative state', 'apallic syndrome' and 'coma vigile'. This clinical characterization is not sufficient. It is necessary to employ additional criteria to distinguish subsets of vegetative patients e.g. computerized tomography, magnetic resonance imaging, single photon emission tomography, electroencephalography, brainstem reflexes, evoked potentials, assessment scales, age, premorbid brain disorders. Diagnostic and prognostic parameters must form the basis for various decisions relating to patients' care and intervention.

Effects of general anesthesia on the human blink reflex

The blink reflex was studied in 10 patients undergoing elective procedures under general anesthesia. Anesthetic agents were isoflurane, halothane, nitrous oxide, methohexital, and thiopental in various combinations. At induction, blink reflexes were diminished by low-dose thiopental (1-1.5 mg/kg) and abolished by high-dose thiopental (4-8 mg/kg) and methohexital (1.5 mg/kg). Blink reflexes were absent during halogenated volitile inhalational anesthesia and did not return until patients were in the recovery room, well after end-tidal anesthetic levels were zero by mass spectroscopy. Recovery of consciousness and the ability to blink on command often preceded return of any blink reflex activity, indicating that the blink reflex is not useful as a postoperative test of facial nerve function in the operating room after anesthesia. In six patients, blink reflexes were still diminished 2-3 hours after cessation of anesthesia, at a time when patients were fully oriented and corneal and eyelid reflexes were clinically normal. This finding suggests that the blink reflex might be a sensitive test of subtle CNS dysfunction after inhalational anesthesia and potentially could serve as a useful objective indicator of recovery from anesthesia for outpatient surgery.

Electrically elicited blink reflex and early acoustic evoked potentials in circumscribed and diffuse brain stem lesions

In the present paper, the function of the brain stem in patients with brain stem lesions of various aetiology is investigated with electrophysiological methods. The clinical observations are supplemented by experimental investigations on cats, in which the blink reflex and the early acoustic evoked potentials were registered during the acute elevation of intracranial pressure. The findings in patients with circumscribed space-occupying lesions in the posterior fossa document that the registration of the BR and the BAEP have a functional diagnostic significance above and beyond the neurological and radiological investigation. In the case of the cerebellar space occupations, specific alterations could not be observed. On the contrary, the alterations of BR and BAEP indicate a general disturbance of brain stem function, possibly as a result of a general increase of intracranial pressure. In cerebellopontine angle tumours, both BR and BAEP showed specific alterations which were usually asymmetrical. The BR changes ipsilateral to the tumour are of major topodiagnostic significance, whereas the alterations of the contralateral potential are especially informative in the registration of BAEP. The alterations of BR and BAEP also allow an appraisal of the localization and extent of the lesion in primary space occupations in the brain stem: A pathological R1 indicates a pontine lesion, whereas pathological R2 responses are found in medullary and in oral pontine and mesencephalic lesions. In contrast to cerebellopontine angle tumours, the BAEP tends to show symmetrical alterations in primary brain stem lesions. The prolongations of interpeak latencies correspond to the brain stem segment concerned, and the same also applies to pathological amplitude reduction and deformations of individual potentials. In patients with localized brain stem damage, the reflex pathway of R2 is discussed on the basis of the BR findings. In contrast to the view held up to now that only structures situated caudal of the facial nucleus area are responsible for the genesis of the R2 response, it is assumed on the basis of our own observations that pontomesencephalic structures rostral to the facial nuclei are also important for the genesis of R2. Registration of BR and BAEP in patients with acute diffuse brain stem damage shows that both methods have a high diagnostic and prognostic value. Isolated damage and combined brain stem lesion can be demonstrated and the course can be followed up. Normalization of pathological findings reflects clinical recovery, and conversely a secondary deterioration indicates the presence of complications.(ABSTRACT TRUNCATED AT 400 WORDS)

Evoked potentials and brain stem reflexes

The recording of evoked potentials (EPs) has become one of the most useful functional diagnostic techniques in the neurosciences during recent years. In combination with the neurophysiological investigation of brain stem reflexes (BSRs) EPs provide good information concerning circumscribed and diffuse brain and brain stem lesions. In this article the role of EPs and BSRs will be pointed out with special regard to their use in neurosurgery concerning awake and comatose patients as well. Pathological findings caused by extracerebral factors or due to neurological (systemic) and otological diseases will be discussed from the aspect of differential diagnosis only. Evoked potentials described in this paper are short latency potentials which are related to more or less defined generators in the peripheral and central nervous system. EPs of long latency seem to play a role in cognitive, affective and integrative functions of the central nervous system and they will not be dealt with in this article. In recent years an increasing number of review articles and monographs dealing with several aspects of evoked potentials has appeared [16, 17, 18, 25, 69, 80, 84, 122, 123, 124, 127, 130].

Central somatosensory conduction time and short latency somatosensory evoked potentials in post-traumatic coma

Short latency evoked potentials (SEPs) were elicited by stimulation of the median nerve at the wrist and recorded simultaneously from the neck and the contralateral scalp in 44 comatose patients with signs of brain stem impairment due to head injury. Thirty-four patients were studied in acute coma on day 1 or 2 after brain injury. Twenty-three patients were studied in prolonged coma during days 3-12 after trauma. Six patients were examined in brain death. Brain stem involvement was divided clinically and by CT scan into secondary lesions due to supratentorial mass displacement and primary lesions due to direct violence to the brain stem. The central somatosensory conduction time (CCT) was measured by subtracting the peak latency of the major response from the neck (N14) from that of the primary scalp response (N20). The amplitude ratios (ARs) N20/N14 were calculated for each trace. Further asymmetries and absence of SEP over one or both hemispheres were noted. In cases in coma due to supratentorial lesions CCT and AR were close to normal in patients with good outcome. CCT increased and AR decreased with the worsening of outcome both in acute and prolonged coma. Asymmetries of SEPs indicated moderate or severe final disability. Patients with absent SEPs over one or both hemispheres due to supratentorial lesions died or survived severely disabled (1 case). In patients suffering from primary brain stem dysfunction, confirmed by a normal or slightly abnormal CT scan, prolonged CCT, asymmetric but also absent SEPs were also found in patients with good outcome both in acute and prolonged coma. AR was generally low in these cases. Early appearance of SEPs or early recovery of initially distorted SEPs and decrease of CCT in prolonged coma or during recovery was a favourable prognostic sign. Therefore even absent or severely distorted SEPs should be interpreted cautiously in patients who may suffer from primary brain stem involvement. Scalp SEPs were totally absent in patients with brain death.

Incidence and prognostic value of spindles in post-traumatic coma

One hundred and thirty-three EEGs were analysed from 80 comatose patients with signs of brain stem impairment due to head/brain injury. Seventy EEGs were taken in acute coma on day 1 or 2 after brain injury. Sixty-three EEGs were recorded in prolonged coma 3-12 days after brain injury. Brain stem involvement was divided by neurological signs and by CT scan into secondary lesions due to supratentorial mass displacement and primary lesions due do direct violence to the brain stem. Different EEG patterns were observed, but spindle activity was of special interest. Spindles were classified as typical (easily recognizable, well organized, 12-14 c/sec activity) or atypical (hardly recognizable, distorted form, 6-11 c/sec activity). Furthermore, asymmetries of spindles were noted. The spindles and their alterations were related to different stages of outcome. Spindles were seen in 91% of the EEGs in acute coma and in 30% in prolonged coma. In acute coma due to secondary brain stem involvement a good outcome was heralded by the occurrence of typical symmetrical spindles combined with early stages of secondary brain stem impairment at neurological examination. In cases of primary brain stem involvement typical spindles also suggested a good prognosis despite the observation of serious clinical signs (decerebrate posturing). The percentage of spindle activity decreased, and distortion and asymmetry of spindles increased with the worsening of outcome. Severe intracerebral lesions (confirmed by clinical and CT scan examinations) led to distortion, asymmetry and finally disappearance of spindles. In prolonged coma spindle activity was markedly reduced regardless of the final outcome. When spindles were present atypical and asymmetric forms significantly increased in patients with bad outcome. There were no significant differences in spindle activity in the different outcome categories, if primary and secondary brain stem lesions were compared.